Controlling the size of FCDs by varying the anchoring strength
The lateral diameter of FCDs is determined by the thickness of the smectic film and the magnitude of the planar anchoring strength of the substrate. For a given substrate, possessing a certain anchoring strength, the diameter increases almost linearly with the film thickness, provided the thickness is larger than a certain critical value. Decreasing the anchoring strength decreases the slope of the diameter vs. film thickness relation and increases the value of the critical film thickness. The anchoring strength can be varied by coating the substrate with binary mixtures of silane compounds which induce, as pure agents, homeotropic or planar anhoring, respectively.